Froth breaking apparatus



Oct. 14, 1952 v. c. LORENZ FROTH BREAKING APPARATUS 2 SHEETSSHEET 1 Filed Sept. 7, 1949 FIG I INVENTOR VINCENT CLAVER LORENZ BY 61M m may 6 ATTORNEYS I Oct. 14, 1952 v. c. LORENZ FROTH BREAKING APPARATUS 2 s1-1EE'rs--sHEET 2 Filed se E. '7, 1949 INVENTOR. VINCENT CLAVER LORENZ ATTORNEYS Patented Oct. 14, 195 2 UNITED STATES PATENT OFFICE; v v I "EJ513310. v 1 7 1:1

FROTH BREAKING APPARATUS. Vincent Claver'ilorenz, An'aconda, Mont. .Application'septembcr 7, 1949, Serial No; 114,332

This invention relates to froth-breaking apparatus, and is directed particularlyto the provision of an improved form of apparatus for breaking down froth that tends to form when a flotation concentrate pulp is thickened. It is quite common practice to dewater dilute fiotationconcentrate pulp in a conventional thickener, but not infrequently sufficient residual froth-ingand flotation reagents are present in the pulp ,fed into the thickener so that a substantial. mat .of mineral-bearing froth collects at the surface .of the body of pulp therein. The fpresenceof, such froth in thethickeneris highly objectionable .because it tends to overflow with the clarified water, and the mineral particles it ,carriesare thereby lost from the thickened concentrate.

The present invention provides an improved and highly effective froth-breaking apparatus that is readily installed on thickeners of conventional construction. The new froth-breaking apparatus comprises a launderwhich is mounted in the thickener in a substantially'radial position, its inner end being in communication with the interior of the central feed well of the thickener and its outer end being closed. The launder lies about at the normal liquid level .of the .body of pulp in the'thickener, and is'partially but not wholly submerged in the pulp. One of theside Walls of the launder is formed with a horizontal slot the lower edge of which lies ,justbelow the normal liquid level of the pulp, wherebypul'p may flow continuously through the slot into the launder. A cutter blade is mounted adjacent the slotted side of the 'launder andismovable across the mouth of the slot, in close .proximitythereto, in a plane parallel to the slotted side of the launder, thereby to. break up froth carried on the surface of pulp flowing through theslotlinto the launder. Advantageously the cutter blade is a rotary device which is rotated ina vertical plane closely adjacent the outer surface o'f'the slotted side of the launder. A continuousacting elevator is mounted in the launder adjacent its inner end to lift pulp' out of the launder and over a discharge lip at the inner endthereof into the" thickener feed well, thereby to. enable. pulp to flow continuously in through the slot, A froth-gathering bafile may extend from the closed outer end of the launder to the wau r the thickener tank to direct froth floating on the surface of the pulp toward the cutter blade.

The foregoing and other features of'the new froth-breaking apparatus are described .below with reference to the accompanying drawings, showing a particularly. advantageous form "of the apparatus, in which Yl igl I is an elevation, partially-in section, of a thickener provided'with the froth-breakingape paratus of "the invention;

Fig. 2 is a plan view of the thickener shown in Fig; 1, showingmore clearly the location of the froth-breaking apparatus; v

Fig. 3 is, a .plan view on-an enlarged scale of the froth-breaking apparatus itself;

f Fig. kis' a longitudin'al section through the apparatus, taken. substantially along 'the. line 4-4 of Fig. '3, showing alsoits "rel'ation'itojthe feed'well of the thickeneryand v Fig. dis "a section taken substantia-lly'along line 5-s of Fig.4,

Figs. 1 and 2 show a conventionalthickener l0 'equippedwith the new "froth-breakingapparatus ll of 'theinvention.' The thickener itself comprises a large, relatively shallow, cylindrical tank [2 having a bottom'l't which slopes down from the walls of a tankto -a--central'-pulp discharge spigot [4 for the thickened pulp. About the inside periphery ofthe;tank-l2,- near its upper edge, is an overflow'launder 5 for clari- Referring fied water from which the solid components of the pulp have settled. The tank lfl is spanned by abridge structure lfi for supporting-"the thickener mechanism, an'dtwhich is also "used to provide support for the froth-breakingapparatus of the invention.

' The concentrate. pulp to: be thickened flows into the thickener through-a 'feedlaund'er' l1 which discharges into a centralafeedy. well. l8. The feed. well, whichis openbothattop (and at bottom and which'is suspended fromthe bridge, preventspthe incoming stream of pulp from seriously agitating the ,main body of; pulp in the thickener tank. The thickener tank-is normally filled with pulp to a level-Ldetermined .bythe location of the upperedge ofx-the overflow launder [5. The main body. of pulp. inthe thickener is maintained substantially quiescent, so that the fine, solid particles therein are. given anopportunity to settle to the bottom. A trussed rake mechanism l9, suspended". from and slowly r0,- tated by a central shaft 2B,..rakes the settled solids to the-central dischargev spigot ill. The shaft 20 is rotated'bya worm 2| engaging with a worm gear 22 and driven by -a.belt,.23 .from a countershaft .24, whichinturnis drivenbya motor 25. 1 Y

7 more .particularlyto Figs..,3. to 5,, the new frothbreaking apparatusll comprises. a launder (i. e.,-a trough-like chamberifzfihaving vertical. side walls 21 anda .bottomi28 which jacent the feed Well [8 of the thickener. The inner end of the launder 26 is formed with a pulp-discharge lip 30, and in the form of apparatus shown in the drawings the inner end of the launder is mounted in place by pivotally supporting the discharge lip on a wall of the feed well I8. This wall of the feed well is formed with a slot 3|. in which the discharge lip 30 is received, and of sufficient depth so that the discharge lip lies about at the normal liquid level L of the pulp. The outer end 29 of the launder is suspended by a bracket 32 attached to a tie rod 33 fastened in turn to the bridge structure I 6. This support for the outer end of the launder is made vertically adjustable by the provision of nuts 34 engaging the threaded lower end of the tie rod and clamping the bracket 32 between them, thereby to permit movement of the launder through an arcuate path in a vertical plane about the pivotal support" of the pulp-discharge lip 30 on the wall of the feed well, and so make it possible to adjust'the position of the launder vertically relative to the liquid level L of the pulp in the thickener.

' One of the side walls 21'v of the launder is formed with a substantially horizontal slot 35 which extends throughout most of the length of the launder. The lower edge 36 of this slot lies just below the normal Qle VelLjof the pulp, so that pulp is enabled to flow continuously through the slot into the launder. To assist inbreaking up froth floating onthejsurface of the pulp flowing into the launder, a rotary cutter blade are, provided. The cutter blade is mounted 'on the end of a horizontal shaft 38 journalledin bearings 39 fastened to the side walls or the launder, and so may be rotated in a vertic'alplane in close proX'- imity to the slotted side wall of the launder and to the mouth of the slot '35.

Mounted in the launder at its inner end adjacent the thickener feed well i8 is a pulp elevator lll of the paddle wheel type. The elevator comprises a hub 4| secured to a horizontal shaft 42 and provided with-a series of radial pulp lift ing paddles 43. By rotating the elevator wheel 40 in thedirection indicated bythe arrow, pulp in the launder is propelled-toward the feed well l8 and is lifted sufficiently to discharge it over the discharge lip 30 into the feed well. The elevator assembly is covered'by ahood 44 to prevent it from splashing pulp into the main body thereof in the thickener.

Both the pulp elevator 40 and the cutter blade 31 are driven from a countershaft 45. The shaft 42 of the elevator is connected directly to the countershaft 45 by means of a sprocket chain 46 engaging sprocket wheels 4! and 48 on the countershaft and on the elevator shaft, respectively; and the cutter blade shaft is indirectly connected to the countershaft byfla sprocket chain 49 engaging sprocket wheels 50 and "on the cutter blade shaft and on the elevator shaft, respectively. The countershaft 45 isprovided with a jpulley wheel 52 by which it is belt-driven from the same countershaft 24: through which th thickener rake mechanism is actuated.

' "Operation of the apparatus is as follows: The slow rotation of the rake structure 19 at the bottom of the thickener tank l2 imparts a slow rotary motion (in the direction of the arrow in Fig. 2) tothe body of pulp. The action of the rake in imparting such rotary motion may be augmented, if desired-by directing small jets of water against the surface of the pulp; at an acute angle thereto near-the periphery ofthe thi kener tank. There.-

' froth-breaking apparatus. The baffle 53 of course is positioned so that it lies partially submerged in and partially extending above the body of the pulp.

As the pulp fiOWs through the slot 35, it carries the floating froth under the cutter blade 31, which is advantageously rotated at, say, about 25 R. P. M. To a considerable extent, the froth is broken down mechanically by the action of the cutter blade. -A continual inflow of pulp into the launder'of the froth-breaking apparatus, and hence a continual now of froth through the plane of rotation of the cutter blade, is assured by rotation of the pulp elevator, which continuously discharges pulp from the launder over the discharge lip 30 into" the feed well of the thickener, whence'it flows downwardly into the main body of pulp well below the surface thereof. Since the dischargelip 30is in about the same hori zontal plane as the lower edge 36 of the slot 35, the elevator does not have to lift thepulp very much to assure continuous inflow thereof through the slot. "Any froth'still persisting after passing by the cutter blade is subjected to the mechanical froth-breaking action of the elevator, and thereafter to the froth-breaking agitation which takes placeiwlthin the feed Well due to the continual inflowof'fresh pulp through the launder ll 'andi'of circulated pulp flowing over the discharge lip. 30 of the froth-breaking apparatus.

' The new froth-breaking apparatus has been found tobe' highly effective in actual use. A lJorr-type thickener equipped with froth-breakmg apparatus' 'of the character described and used to thicken a zinc-lead sulphide flotation concentrate'practically eliminated the froth mat that 'had'persistentlyfloated on the surface of the pulpinthe thickener prior to installation of the froth-breaking apparatus. coincidentally, the amount of'zinc'lost in the thickener overflow was reduced by over 4000 pounds per month, and the amountof lead lost similarly was reduced by over v1000 pounds per month. Equivalent froth-breaking efficiency and savings in mineral values can be obtained when the new frothbreaking apparatus is used in combination with thickeners employe'din the dewatering of other froth flotation concentrate pulps.

' I claim:

.1. The combination with a thickener adapted to be filled with a body of pulp to a normal liquid level and having a central pulp feed well, of fro'th breaking apparatus which comprises a launder communicating at its inner end with the inter or of the feed Welland projecting outwardly therefrom, saidlaunder' being closed at its outer end and being positioned about at the normal liqu d level of the pulp, one of the side walls of sa d 'launderbeing formed with a horizontal slot the lower edgeof which lies just below the normal liquid level of'the'pulp, whereby pulp may flow continuously through said slot into the launder, a rotary cutter blade mounted for rotation closely adjacent the slotted side of the launder and movable across the mouth of the slot in a plane substantially parallel to the plane of the slotted side of the launder, thereby to break up froth carried on the surface of pulp flowing into the launder, and an elevator mounted in the launder adjacent its inner end for lifting pulp out of the launder and into the feed well.

2. Apparatus according to claim 1, characterized in that the inner end of the launder is pivotally supported on a wall of the feed well, and further characterized in that the outer end of the launder is held in place by a vertically adfroth-breaking apparatus which comprises alaunder closed at its outer end and communicating at its inner end with the interior of the feed well, said launder being partially submerged in the body of pulp when the thickener is filled with pulp to its normal liquid level, one side wall of the launder being formed with a horizontalslot the lower edge of which lies just below the normal liquidlevel of the pulp, whereby pulp may flow through the slot into the launder, and the bottom of the launder being sloped downwardly in the direction of the feeding well, a rotary cutter blade mounted for rotation in a vertical plane closely adjacent the outer surface of the slotted side of the launder, thereby to break up froth carried on the surface of pulp flowing into the launder, a froth-gathering baffle extending horizon-tally from the closed end of the launder to the wall of the thickener for directing froth floating on the slowly rotating pulp body toward the rotary cutter blade and the slot in the side wall of the launder, and a rotary elevator wheel mounted in the launder adjacent its inner end for lifting pulp out of the launder and into the feed well.

4. Froth-breaking apparatus of the character described comprising a launder having a substantially horizontal pulp inlet slot in one of its side walls, a rotary cutter blade mounted for rotation closely adjacent said slotted side wall and movable across the mouth'of the slot in close proximity theretoand in a plane substantially parallel to the plane of the slotted side, thereby to break up froth carried by pulp entering through,

mounted in the launder adjacent said lip for lifting pulp thereover and out of the launder.

5. Froth-breaking apparatus of the character described comprising a launder having a substantially horizontal pulp inlet slot in one of its side walls, a rotarycutter blade mounted for rotation in a vertical plane in closeproximity to the mouth of the slot, thereby to break up froth carried by pulp entering through the slot into the launder, :a pulp discharge lip at one end of the launder and in substantially the same horizontal plane as the lower edge of the slot, and an elevator mounted in the launder adjacent said discharge lip, whereby pulp entering the launder through the inlet slot may be lifted sufiiciently to be discharged over said discharge lip.

6. Froth-breaking apparatus of the character 1 described comprising a launder having a bottom sloping downwardly from one end to the other and having a substantially horizontal pulp inlet slot in one of its side walls, a rotary cutter blade mounted for rotation across the mouth of said slot in close proximity thereto and in a plane VINCENT CLAVER LORENZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 7 Date 1,439,407 Elrod Dec. 19, 1922 2,037,725 Scott y 0, 37

FOREIGN PATENTS Number Country 7 Date 633,942 France Oct. 31, 1927 136,359 Switzerland Jan. 2, 1930 536,259

Germany Oct. 21, 1931 

